(1) Field of the Invention
The invention relates to a tool for shaping, by deep drawing, a truncatedly ending orifice in a metallic strip material, viz. for manufacturing a faceplate for a locking fitting or the like for a door, window or the like, comprising at least a punch and a die. The invention also relates to a faceplate comprising at least a truncatedly ending orifice shaped by deep drawing by means of this tool.
As appears above, this invention in particular relates to the field of the building ironmongery.
(2) Description of the Prior Art
Many fittings, viz. locking fittings, include a faceplate for covering the organs of the locking mechanism, viz. an actuating rod that is accommodated e.g. in a groove provided for at the periphery of a leaf corresponding to a door, window or the like. Such faceplates are kept in place by means of fixing organs, such as screws, that pass through the faceplate to penetrate into the carpentry while passing, should the case arise, through an elongated opening provided for in an actuating rod.
In order not to create, at the level of the visible external face of the faceplate, an obstacle likely to hinder the actuation of the leaf or that would require to increase the backlash at the level of the fillister of this leaf with respect to the sash-frame, the screws usually used are of the sunken-head type, whereby they are accommodated in the truncated end of the orifice for the passing through of the screw present in the faceplate.
Therefore, when shaping this faceplate, several such troncatedly ended orifices have to be provided for alongside this latter, which presently arises a problem, since it is known that this is to be carried out under high-rhythm manufacturing circumstances. Thus, the solution of a machining in the form of a boring followed by a milling is not suited at all for such production rhythms. As a matter of fact, such faceplates are usually shaped by deep drawing, which solution is much better suited for this case. The deep drawing of a strip material having a small width and a small thickness is however a delicate operation to be performed and often results in problems of distortion, in particular when the machining to be carried out does not consist of a mere operation of removal of material through cutting out.
By way of an example, though no difficulty arises for the provision of an orifice in a faceplate, because this indeed results in a mere removal of material, the provision of a truncated end at the level of this orifice results into a creep of material, thus often into a change of the outer sizes of the faceplate. Thus, if this creep of material is not restrained, the faceplate gets a slightly increased width at the level of a truncatedly ended orifice resulting from a deep-drawing process. Finally, this may result in difficulties when mounting this faceplate.
There has already been conceived a process capable of ensuring the control of the creep of material resulting, in particular, from the machining, through deep drawing, of the truncated end corresponding to an orifice previously provided for in a strip material having a small width and a small thickness.
As a matter of fact, this process consists of making in this strip material first of all an orifice the cross-section of which is slightly larger than that it must finally have. Then, during a second operation, the truncated end is made by means of a correspondingly shaped punch, which results into a creep of material in the lower portion of the orifice towards the axis of this latter the cross-section of which therefore becomes smaller. This creep of material is kept under control by means of a die including, on its upper face, a circular crown having a triangular cross-section the apex of which is oriented towards the lower face of the strip material to be shaped and which defines, during the deep-drawing operation, a circular groove concentrical to the orifice on this lower face of the strip material.
As results from the preceding description, this process has the drawback that one has to proceed in two steps, which, of course, results in a loss of time applied to faceplates for fittings, such as locking fittings or the like, and this results into a limited production rhythm.
In addition, it should be observed that the final cross-section of the orifice depends on the thickness of the strip material, this assuming the travel of the truncatedly shaped punch corresponds to an invariable value. Therefore, one understands that it is impossible to accurately adjust this cross-section of the orifice serving as a passageway for the fixing screw.